1) Field of the Invention
The present invention relates to releasable stores that are mounted on an aircraft and, more particularly, to a store ejection system, store, and associated method that use a pressure vessel integral to the store as an energy source for ejecting the store from the aircraft.
2) Description of Related Art
The term xe2x80x9cstorexe2x80x9d is used herein to refer generally to any of a number of munitions or other materials that can be dispensed from an aircraft. For example, military aircraft can include a store ejection system to dispense bombs, missiles, rockets, and other types of munitions. Non-munitions stores can include electronic equipment and other materials. Typically, the store ejection system includes one or more racks beneath the wings or fuselage of the aircraft for holding the stores and releasing the stores upon a command. For example, store racks are described in U.S. Pat. Nos. 5,907,118 and 6,035,759, both by the same inventor and assignee as the present invention.
In one conventional store ejection system, the stores are connected to the racks by one or more mechanical hooks. The store ejection system includes a release mechanism for actuating the hooks to release the stores and a jettison mechanism for forcibly ejecting the stores away from the aircraft. The jettison mechanism can include a pressure-actuator, such as a ram that is actuated by a pressure increase in a cylinder. In the conventional system, the pressure is generated by a pyrotechnic cartridge, i.e., an explosive. Ignition of the pyrotechnic cartridge initiates a chemical reaction that generates a high pressure, which can be used for actuating the release mechanism and the jettison mechanism.
Although such pyrotechnic cartridges provide a weight efficient unit for storing and releasing energy, the cartridges present a number of maintenance, reliability, and safety concerns. For example, the chemical reaction of the explosive charge in the cartridge generates a large amount of residue. Some of the residue is deposited in the ejection system where it can clog or otherwise interfere with the components of the ejection system. Moisture and corrosives in the residue can also damage the ejection system. Additionally, moisture deposited in the ejection system can freeze or gather additional debris. To avoid unreliability and possible failure, the ejection system must be disassembled and cleaned regularly, thus increasing the cost and downtime for maintaining the system. Such cleaning often requires the use of hazardous cleaning solvents that require care in storage, use, handling, and disposal. Further, due to the pyrotechnic nature of the cartridges, special storage and handling precautions for the cartridges are necessary. For example, ground crew personnel must use special equipment to conduct stray voltage checks before installing the cartridges to prevent inadvertent firing. Also, unspent cartridges must be removed before unloading unreleased stores from the aircraft.
Non-pyrotechnic ejection systems have been proposed, such as the pneumatically-driven store ejection system described in U.S. Pat. No. 5,583,312, which is also by the same inventor and assignee as the present invention. That device does not require pyrotechnic cartridges, but instead includes a compressor for compressing a non-pyrotechnic gas that is then used to actuate ejector pistons of one or more suspension and release equipment (S and RE) modules that releasably retain and jettison stores. The pressurized gas, which can comprise ambient air, does not deposit a significant amount of residue on the system components. Thus, the residue build-up and corrosion resulting from pyrotechnic chemicals are eliminated and the maintenance required on the system is minimized. However, the compressor adds to the initial cost of the system and the recurring costs for overhauling and maintaining the compressor. The compressor also adds to the overall weight of the system. Further, the compressor requires the availability of sufficient power from the aircraft""s electrical or hydraulic systems to drive the compressor motor. In addition, the compressor must generate sufficient pressure to release the stores, so the compressor requires an interval of time for preparing the release of the store. The time required to achieve a sufficient pressure is dependent on the compressor, the number and size of ejector racks that are connected to the system, and the air density, which varies with altitude. Therefore, the release of the stores can be delayed while the compressor generates the required pressure.
There have also been proposed ejector devices that use a stored volume of compressed gas to provide the energy for ejection. For example, U.S. Pat. Nos. 4,095,762 and 4,905,568 to Holt and Hetzer et al., respectively, each describe an ejector mechanism that uses a pressurized gas as the energy source for ejection and a hydraulic fluid, which acts as the energy transfer mechanism for ejection. Both patents describe that the hydraulic fluid can be used to re-pressurize the gas after ejection. Holt specifies that the action of recocking a piston moves the hydraulic fluid and thereby re-pressurizes the gas. Hetzer recites that after ejection, a pump is used to pump the hydraulic fluid, and the hydraulic fluid thereby acts on the gas to re-pressurize it. Therefore, neither patent requires a compressor for re-pressurizing the gas. However, the hydraulic systems add weight and complexity to the system. Further, the pump of Hetzer for pumping the hydraulic fluid adds weight, power, and timing concerns similar to those discussed above in connection with the compressor of U.S. Pat. No. 5,583,312. Similarly, in the case of Holt, some additional device would be required for recocking the system.
U.S. Pat. No. 4,204,456 to Ward discloses a pneumatic bomb ejector that uses a pressurized gas from a storage container for the energy required to eject the bomb. However, no specific storage container is described, and there is no description regarding how and when the storage container is pressurized. Pressurizing the container during flight would require a pressurization device, such as a compressor, again with the weight, power, and timing concerns noted above. Alternatively, if the storage container is pre-pressurized before the aircraft takes off so that no on-board compressor is needed, the pressure in the storage container will fluctuate as the temperature of the gas in the storage container changes with the ambient temperature. Further, the pressure in the storage container will not be affected by changes in the ambient pressure. Thus, the differential in pressure between the storage container and the ambient air will change as the aircraft changes altitude, thereby changing the operational characteristics of the ejector and possibly resulting in incorrect or failed ejections. Additionally, refilling the container before take-off would require that the container be connected to a refilling device, which could delay the flight.
Thus, there is a need for a store ejection system and method that use a non-pyrotechnic gas as the source of energy and transfer mechanism for jettisoning a store from an aircraft. The system should not require the use of pyrotechnic reactions or an on-board compressor system. Preferably, the system should not require a long time delay to achieve pressurization. Additionally, the system should require little or no power from the aircraft""s electrical or hydraulic systems for pressurizing the gas.
The present invention provides an improved store ejection system for mounting a jettisonable store on an aircraft. The system includes a pressure vessel integral to the store, which is capable of holding a pressurized non-pyrotechnic fluid for providing the source of energy and the transfer mechanism. For example, the pressure vessel can define an interior space of between about 20 and 50 cubic inches and can be pressurized to between about 3,000 and 10,000 psi. A releasable seal, including a valve or a burst portion, is configured to hermetically and releasably seal the pressure vessel. An actuation system includes an accumulator releasably connected to the pressure vessel for receiving and storing the fluid from the pressure vessel, a dump valve for controlling a flow of fluid from the accumulator, and a controller for actuating the dump valve to an open position in response to a control signal to jettison the store. A pneumatically-driven jettison mechanism releasably retains the store. The jettison mechanism is fluidly connected to the dump valve such that actuating the dump valve to the open position releases the pressurized fluid in the accumulator to flow to the jettison mechanism, thereby actuating the jettison mechanism to jettison the store.
The releasable seal is configured to hermetically seal the pressure vessel before the actuation system is connected to the pressure vessel. Upon release of the releasable seal, the actuation system is fluidly connected to the pressure vessel. For example, the seal can be released by an actuator that is actuated by a controller. The jettison mechanism can include at least one hook for releasably retaining the store and at least one ejector piston for forcibly jettisoning the store away from the aircraft when the hook has been actuated to a release position. The hook and the ejector piston are actuated by the pressurized fluid exiting the accumulator through the dump valve. A store present switch can be configured to detect if a store is retained by the jettison mechanism and to transmit a signal to a controller to indicate if a store is present. A relief valve can be configured to vent the fluid from the accumulator to reduce the pressure in the accumulator to below a maximum operating pressure.
According to one aspect of the invention, a quick disconnect connection device releasably and fluidly connects the pressure vessel to the actuation system. The connection device can include a flexible tube for fluidly connecting the pressure vessel to the accumulator and an electrical conductor for providing electrical communication between the aircraft and the store.
The present invention also provides a store configured to be jettisoned from an aircraft using a fluid as the source of energy and the transfer mechanism. The store includes a pressure vessel that is integral to the store and capable of holding a pressurized non-pyrotechnic fluid for providing the source of energy and the transfer mechanism. For example, the pressure vessel can define an interior space of between about 20 and 50 cubic inches, and the fluid in the pressure vessel can be compressed to between about 3,000 and 10,000 psi. A releasable seal, such as a valve or burst portion, is configured to hermetically and releasably seal the pressure vessel. The store is configured to be connected to the aircraft such that upon release of the releasable seal, the pressure vessel is fluidly connected to an actuation system of the aircraft and the fluid flows from the pressure vessel to the actuation system. According to one aspect of the invention, an actuator is configured to release the releasable seal. The actuator can be connected to the aircraft by an electrical connection that is configured to be connected to a quick disconnect connection device. A pneumatic connection can also be configured to be connected to the quick disconnect connection device for fluidly connecting the pressure vessel to the aircraft.
The present invention also provides a method of jettisoning a store from an aircraft using a pressurized non-pyrotechnic fluid from the store as the source of energy and the transfer mechanism. The method includes releasably retaining the store with at least one pneumatically-driven jettison mechanism and releasably and fluidly connecting an actuation system to a pressure vessel of the store. The pressure vessel can be pressurized before being connected to the accumulator and hermetically sealed with the releasable seal. The releasable seal is released, for example, by communicating an arm control signal to a controller, which responds by destructively releasing a burst portion of the releasable seal so that the pressure vessel is fluidly connected to the accumulator. The accumulator is fluidly connected to the jettison mechanism by actuating a dump valve to an open position. The dump valve is fluidly connected to the accumulator such that opening the valve allows fluid to flow from the accumulator to the jettison mechanism and actuate the jettison mechanism to jettison the store with the integral pressure vessel. A relief valve fluidly connected to the accumulator can be opened to vent the fluid from the accumulator when an over-pressure condition is detected in the accumulator or when it is desired to disarm the jettison mechanism.
According to one aspect of the invention, the store is releasably retained with at least one hook, which is actuated to an open position to release the store. The accumulator can also be connected to at least one ejector piston so that the fluid flowing from the accumulator actuates the piston to jettison the store.
Thus, the present invention provides a store ejection system, store, and method that use a non-pyrotechnic fluid as the source of energy and transfer mechanism for jettisoning the store from an aircraft. According to one aspect of the invention, the pressure vessel is integral to the store and does not require power from the aircraft""s electrical or hydraulic systems for pressurizing the fluid. According to another aspect, the integral pressure vessel provides the pressurized fluid to the ejection system without requiring a long time delay to achieve pressurization and without requiring the use of pyrotechnic reactions or an on-board compressor or storage container.